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Frozen in Time
Imagine a world where life has been pushed to its limits. Where the life is nothing like anything you've ever seen, yet looks vaguely familiar. Where ice rules the world, and barely an inch of liquid water covers the ocean. Imagine a world frozen in time. Snowball Earth What was the driving force of evolution during the Phanerozoic eon? None else than the recovery from the snowball earths of the Cryogenian. But this recovery was lucky, and if the large amounts of volcanism signaling the end of the Cryogenian and the dawn of the Ediacaran didn't happen in time, the world would be stuck with an ocean surface as hard as rock. All animal life could perish, and the Precambrian would never end. What if this was the case? I will lead you through a though experiment which shows what may have happened if the Cryogenian glaciations lasted until the Triassic of our timeline. In this world, volcanism and CO2 are at zero and 50 ppm respectively. This is because the buildup and breakup of the supercontinent of Rodinia have stopped plate tectonics almost completely. The split happened not at the end of the Cryogenian, but at the end of the Hadean eon, after the formation of the Earth. The Late Heavy Bombardment lasted less than 1 million years because of a random change in Jupiter's orbit which stopped it from staying in sync with Saturn. The Earth cooled much more quickly, and this had an effect on plate tectonics. Starting about the same as the plate tectonics in our timeline, the process slowed down because of the quicker cooling of the Earth, and by the breakup of Rodinia, this had accumulated enough to stop volcanism. The CO2 dropped quickly, and the Cryogenian glaciations became yet more severe, and without break. Life on Earth In our oceans, we see familiar creatures like crustaceans, jellyfish, and sponges. But this is no familiar ocean. These are, in fact, these are the only familiar creatures. Trilobites are no less diverse than they were in our timeline, but the most diverse group of all is the Ediacara biota. Other than arthropods, the only other bilaterian animals are "monoplacophoran" basal molluscs. Life has taken an insane and alien path of evolution. The majority of animals are semiaquatic and ice-loving. Crustaceans are represented by krill-like forms, which aren't too different from Home Earth, but also by predatory, terrestrial, long-legged forms, some of the apex predators of this world. The trilobites are mostly benthic, there being little ice on the sea floor, but a select few make up the only flying fauna of this Earth, insect-like trilobites. As for the huge stem-arthropods like Anomalocaris, they went extinct due to their unadaptability to change with the ever-growing ice sheets and stranger, harder to catch prey. The Ediacara biota have stayed on par with animals here, having evolved first, and evolved to deal with the snowball earths. Often, they are mistaken for animals, such as an eyed Dickinsonia-line Ediacaran being nearly identical to a trilobite, despite being unrelated protozoans forming a monophyletic lineage, the kingdom Vendozoa. While never predators of this world, and sometimes even looking like algae, they are more diverse and flexible than animals. When a radiation of non-planktonic, predatory jellyfish occurred, the Ediacara biota quickly responded by in many unrelated groups evolved sting resistance and absorption. Sponges are nearly identical to those on Home Earth, and this is because of the extremely slow evolution of early animals. Molluscs are fairly common, but generally all in a sessile, hard-shelled form, this being difficult for any predators of this world to eat. While jawed vertebrates would normally feed on these molluscs, they are absent, in fact, chordates had not yet evolved by "second split", when the glaciation became colder and without break. The jellyfish have conquered this world's oceans, and despite them absolutely lacking any intelligence in our timeline, here they have evolved predatory strategies, including camouflage, speed, and stealth. On land, the first of the Terramedusae, a class of semiaquatic to terrestrial jellyfish, slid on their tentacles on the ice covering the oceans, until they had mastered moving around using nothing but a unique sliding speed mechanism. The relatives of the jellyfish, the Anthozoa, were not adaptable enough to survive, and their sessility and failed predation tactics made them fall victim to a combination of being excessively preyed on and frozen to death. History Hadean to Mesoproterozoic The Late Heavy Bombardment was a time in which the Solar System had nearly settled after its formation. The Earth had already accumulated its moon, the planet Theia was gone, and life was destined to begin. In our timeline, a sync in the orbit of Jupiter and Saturn meant that for 200 million years the Earth was an inferno, completely inhospitable, a time when every square centimeter of the Earth was hit by an asteroid or comet. For every two times Jupiter orbited, Saturn orbited once, meaning that every 30 years or so a huge gravitational force sent comets and asteroids towards the inner planets. This affected the outer planets too. Jupiter was sent inwards towards Mars, while all of the planets past Jupiter were sent outwards. Neptune and Uranus switched places multiple times, before finally settling in their current positions. In this timeline, a huge star passed inside of the Oort Cloud, giving all of the gas giant planets a small tug, enough to destabilise the sync with Jupiter and Saturn, but little enough so that in this timeline Uranus is the furthest planet from the sun. Plate tectonics kicked in on Earth, but eventually slowed down from a lack of heat produced by the asteroids impacting Earth. The course of life was relatively the same, starting 3.9 billion years ago as while the hospitable Earth had come into existence sooner, the essential building blocks of life had come together later, being scarcer from the lack of comet impacts. Throughout the Archaean and the majority of the Proterozoic, the course of life seemed identical to our timeline. But by the breakup of the supercontinent of Rodinia, plate tectonics came to a halt, and the Earth's continents were essentially locked in the V-shaped supercontinent Pannotia. Category:Alternative Evolution